Plaque placed on the volcano Ok commemorating the first vanished Icelandic glacier.

Rice University/Dominic Boyer/Cymene Howe

Okjökull glacier was pronounced virtually dead by scientists in 2014 when the ice was no longer thick enough to move. Located northeast of the Icelandic capital of Reykjavik atop of a volcano named Ok, the glacier – or jökull in Icelandic – lost most of its ice mass due to warming temperatures as a result of human-caused climate change.

This weekend prime minister Katrin Jakobsdottir commemorated the doomed glacier by joining scientists and other politicians for a memorial and putting a plaque on the mountain. The “letter to the future” written by Icelandic author Andri Snaer Magnason on a copper plaque, ends with the date of the ceremony and the actual atmospheric concentration of carbon dioxide – with 415 parts per million the highest level in modern human history. In an interview with the BBC Magnason explained the message as “a big symbolic moment. Climate change doesn’t have a beginning or end and I think the philosophy behind this plaque is to place this warning sign to remind ourselves that historical events are happening, and we should not normalize them. We should put our feet down and say, okay, this is gone, this is significant.”

Comparing photographs and surveys spanning the past 50 years, glaciologists noticed in 2003 that more snow was melting at Okjökull than needed to sustain the glacier. A geological map from 1901 estimated Okjökull spanned an area of about 15 square miles (38 square kilometers). In 1978, aerial photography showed the glacier was 1,1 square miles. Today, less than 0.3 square mile remains. A survey in 2014 confirmed that the remaining ice thinned so much that the former glacier no longer has enough mass to flow.

Landsat satellite image of Okjökull in September 1986.

NASA Earth Observatory

… and in August 2019.

NASA Earth Observatory

As snow transforms into ice and pressure on the basal layers builds up, deformation of ice crystals and partial melting result in the glacier creeping and sliding downslope. If a glacier loses enough mass, the pressure decreases until the ice will no longer move. This limit is used by glaciologists to distinguish between a glacier and inactive icefield.

Ice covers about 10 percent of Iceland. An inventory of glaciers in the year 2000, listed just over 300 scattered across the island. By 2017, 56 of the smaller glaciers had disappeared. Depending on the rise of temperatures in the next century, an estimated 40-60 percent of the remaining ice could vanish.